When a display device is displaying, it needs to utilize a shift register to implement scanning of a pixel unit. The shift register comprises multiple stages of shift register units, each of which is corresponding to one row of pixel units. Progressive scanning drive of the pixel units of the display device is realized by the multiple stages of shift register units, so as to display an image.
In the shift register, each stage of shift register unit is constituted of a plurality of thin film transistors, and signals in the shift register unit are transmitted by respective thin film transistors. However, a threshold voltage of a thin film transistor is easily influenced by degree of stability and temperature in the manufacturing process. Under the condition of instability, high temperature or low temperature in the process of manufacturing, the threshold voltage of the thin film transistor would change dramatically, such that a signal of a pull-up control node and a signal of a pull-down control node in the shift register unit are distorted, thereby causing that signals output by the shift register unit are distorted seriously, or sometimes even causing that the shift register unit cannot output signals. As a result, the display effect of the display device is reduced.